As the treatment method which is conducted aiming at removing an environmental pollutant or a toxic substance contained in a feed or a feed raw material in the processing and production processes of a feed for animals or a raw material thereof, methods disclosed in Patent Documents 1 and 2 can be given as representative examples.
Patent Document 1 discloses a technology in which an aliphatic acid ester, an aliphatic acid amide, free aliphatic acid or a hydrocarbon, which are volatile operation fluids, is added to a fat or oil which contains an environmental pollutant or a toxic component, and the fat or the oil and the volatile operation fluid are together subjected to a stripping treatment, whereby an environment pollutant or a toxic component is separated from the fat or the oil. Here, the stripping treatment means a treatment for removing a specific substance which is desired to be removed from a fluid by the following methods. A vapor or a gas is blown to a fluid which contains a specific substance to be removed; a highly-volatile fluid mixed, followed by evaporation of the fluid; a fluid which contains a specific substance to be removed is entirely brought into a vacuum state, whereby the specific substance is allowed to move to a vapor phase, a gas phase or a volatile fluid phase; or a specific substance itself is evaporated.
The technology disclosed in Patent Document 2 is aiming at removing phytic acid contained in cereal served as a feed or a food. If an animal intakes a feed or a food which contains phytic acid in a high concentration, normal intestinal absorption of trace metals which are nutritionally important is inhibited, causing a series of deficiencies. Therefore, it is required that the phytic acid be removed from a cereal which contains thereof. In this conventional technology, a cereal containing phytic acid such as soybean oil cakes is inoculated with Aspergillus oryzae to produce Koji, and a phytic acid-decomposing enzyme such as phytase or phosphatase which is produced during the proliferation process of the Aspergillus oryzae is utilized to remove by decomposition of the phytic acid in the cereal.    Patent Document 1: JP-B-3905538    Patent Document 2: JP-A-H08-214822